1. Field of the Invention
This invention relates to pumps and is particularly directed to a composite impeller for use in centrifugal coal slurry pumps and the like.
2. Description of the Prior Art
In attempting to overcome the energy crisis, numerous techniques have been proposed for converting coal into oil, gas or the like. Most of these techniques involve pulverizing the coal and combining it with a suitable fluid to form a slurry which is transported through the process by pumping. Unfortunately, such slurries are extremely abrasive and tend to jam piston pumps, while the slurries act like a stream of sandblast on centrifugal pumps, causing high maintenance and greatly reducing the life of the pump. Moreover, coal slurries tend to be highly carcinogenic so that frequent maintenance of the pumps involves a serious health hazard. Moreover, coal conversion processes generally require that the coal slurries be maintained at temperatures of 300.degree.-600.degree. F. Few impeller materials can withstand such temperatures. It has been proposed to form the pump components of high temperature and wear-resistant materials, such as tungsten carbide and the like. However, such materials are expensive and extremely difficult to fabricate, causing the cost of such pumps to be prohibitive. Thus, no satisfactory solution to this problem has been found in the prior art.